US3185202A

US3185202A - Burner for a boiler

Info

Publication number: US3185202A
Application number: US279463A
Authority: US
Inventors: Gerald T Mitchell; Jr Richard Cunningham
Original assignee: Vapor Corp
Current assignee: Vapor Corp
Priority date: 1963-05-10
Filing date: 1963-05-10
Publication date: 1965-05-25
Anticipated expiration: 1982-05-25
Also published as: AT256303B; GB1038159A; CH422205A; ES291185A1

Description

y 1965 e. 1'. MITCHELL ETAL 3,185,202

BURNER FOR A BOILER Filed May 10, 1963 2 Sheets-Sheet 1 FIG.\

ATTORNEY May 25 1965 G. T. MITCHELL ET AL 3, 5,202

BURNER FOR A BOILER Filed May 10, 1963 2 Sheets-Sheet 2 33 F 16. 5 F166 INVENTORS GERALD T. MITCHELL.

B RICHARD CUNN] GHA R. Jib-M ATTOR NEY United States Patent 3,185,202 BURNER FOR A BOILER Gerald T. Mitchell, Wilmette, Ill., and Richard Cunningham, (in, Houston, Tex., assignors to Vapor Corporation, Chicago, Ill., a corporation of Delaware Filed May 10, 1963, Ser. No. 279,463 7 Claims. (Cl. 158-4) This invention relates in general to a burner for a boiler or a steam generator, wherein the burner provides the heat source that is capable of furnishing the hot gases necessary to produce the output of the boiler or steam generator.

The burner of the present invention comprises a fire pot composed of a refractory lined metal can or body having a plurality of circumferentially spaced combustion throats. A burner nozzle is mounted at each throat and arranged to direct its spray pattern across the spray pattern of an adjacent burner nozzle. Each combustion throat is constructed to give the maximum pressure drop possible with available combustion air. A plenum chamber surrounds the fire pot and is pressurized for supplying the combustion air to the combustion throats. The structure of the fire pot, the nozzles and their arrangement, and the plenum chamber are such that nearly stoichiometric combustion is achieved. The present invention is especially useful in the burning of heavy grade fuel oils so completely that no smoke is visible.

It is an object of the present invention to provide a new and improved burner for boilers or steam generators.

Another object of this invention is in the provision of a burner for boilers or steam generators, wherein the construction of the burner is compact and much smaller than other burners of comparable heat output.

Still another object of this invention resides in the provision of a burner for boilers or steam generators that is capable of burning heavy grade fuel oils completely with no visible smoke.

A further object of this invention is to provide a burner for boilers or steam generators that includes a fire pot having a plurality of burner nozzles, wherein each burner nozzle is arranged to direct its spray pattern across the spray pattern of an adjacent nozzle so that more complete combustion can be obtained.

A still further object of this invention is in the provision of a burner for boilers or steam generators including a fire pot having a plurality of combustion throats and a burner associated with each combustion throat, and a plenum chamber in surrounding relation with the fire pot, wherein the plenum chamber is pressurized to supply the combustion air to the combustion throats.

Another object of this invention resides in the provision of a burner for boilers or steam generators, wherein the burner includes a fire pot having a plurality of combustion throats that are constructed to give the maximum pressure drop possible with available combustion air.

A still further object of this invention is to provide a burner for boilers or steam generators that includes a fire pot having a plurality of burner nozzles, wherein at least one of the nozzles may be shut off for removal and cleaning without necessitating the shutting down of the burner.

Other objects, features, and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying "ice sheets of drawings, wherein like reference numerals refer to like parts, in which:

FIG. 1 is a front elevational view of the burner and associated elements in accordance with the present invention;'

FIG. 2 is a vertical sectional view taken substantially along line 22 of FIG. 1;

FIG. 3 is a transverse sectional view of the fire pot taken substantially along line 3-3 of FIG. 2;

7 FIG. 4 is a diagrammatic view showing the fire pot in cross section and the spray patterns of the burner nozzles;

FIG. 5 is a top plan view of the fuel nozzle employed in the present invention; and

FIG. 6 is a transverse sectional view taken substantially along line 6-6 of FIG. 5.

Referring now to the drawings and particularly to FIG. 2, the burner of the present invention includes generaly a fire pot 10 enclosed by a housing 11 defining with the fire pot a pressurized plenum chamber 12, and a plurality of burner nozzles 13.

The fire pot 10 generally comprises a refractory lined metal can and includes particularly a cylindrically-shaped body 14 closed at one end by a dome-shaped cover 15, and having a choke 16 at the other end through which the hot gases are discharged from the fire pot and to the coils of a boiler or steam generator. The cover 15 is mounted on the body 10 by means of a plurality of stud bolts 17 welded or otherwise suitably secured to the body 10, and a bracket 18 welded or otherwise secured to the cover 15 and having holes for receiving the stud bolts 17. Nuts 19 are threadedly received on the stud bolts 17 to bear against each bracket 18 and hold the cover in place. A ceramic or otherwise high temperature gasket 20 is preferably arranged between the cover 15 and the body 10.

A plurality of combustion throats 21 are circumferentially and equally spaced in the body 14 of the fire pot 10, each of which has associated therewith a burner nozzle 13. The longitudinal axis of each combustion throat, as represented generally by the line 22, (FIG. 3) is coaxial with the longitudinal axis of each associated burner nozzle and this axis is angularly displaced about 30 from a radial line 23 projecting from the longitudinal axis of the fire pot and intersecting the axis of the throat at the inner wall 24a of the fire pot. Each combustion throat is venturi-shaped to provide the maximum pressure drop possible with the available combustion air. The inner and outer ends of each combustion throat are flared. The throat diameters are flared open at 50 at the inside surface of the combustion chamber, wherein the angle is measured from the nozzle tip as illustrated particularly in FIG. 3.

The throat diameter depends primarily on the combustion air static pressure available. While six combustion throats and associated nozzles are shown in the illustrated embodiment, it should be appreciated that a greater or smaller number of throats and nozzles may be employed depending upon the power output desired from the burner. As can be seen particularly in the diagrammatic view of FIG. 4, the combustion throats and nozzles are arranged so that the spray pattern of one nozzle crosses the spray pattern of an adjacent nozzle and is directed at the alternate adjacent nozzle.

The fire pot defines therein a combustion chamber 24 within which the air and fuel mixture is burned, and thereafter the resultant gases discharged through the choke 16. The length of the choke 16 is approximately 40 percent of the total length of the combustion chamher, while the diameter of the choke is determined by the inside diameter of the boiler coils. In the embodiment illustrated, any two burner nozzles [13 may be turned off, removed for cleaning and/or servicing without substantially affecting the combustion characteristics of the burner, thereby eliminating the necessity of shutting down the boiler while servicing the burner.

A blower 25, FIG. 1, is mounted laterally of the housing 11 and communicates with the plenum chamber 12 by means of a duct 26 for the purpose of supplying the combustion air to the plenum chamber 12 and the fire pot 10. The air delivered from the blower wipes across the outer walls of the fire pot 10, and is thereby preheated prior to entering the'combustion throats 21.

The burner nozzles 13, when delivering light or heavy fuel oils, atomize the oil by means of steam, air or fuel pressure. The combustion air supplied to the nozzle area and through the combustion throats 21 mixes with the atomized fuel as it is sprayed from the burner nozzles. The particular nozzle direction produces a swirling and turbulent mixing action within the combustion chamber which aids in the completion of the combustion process. Moreover, the combustion air is directed within the combustion chamber in such a manner that no fuel impinges upon the inner walls of the combustion chamber, and the fuel-air ratio is relatively uniform throughout the combustion chamber. The combustion throats 21 are located quite close to the closed end of the combustion chamber as noted particularly in FIG. 2.

An opening 27 is provided in the center of the domeshaped cover 15, and effectively in the top of the combus tion chamber for the purpose of creating air movement around the cover and to provide a cooling action for the plenum chamber dome.

An air curtain is formed along the inside refractory walls of the combustion chamber by providing a plurality of circumferentially arranged holes 28 extending from the inner end wall 29 to the outer surface of the outer wall 30 as seen in FIGS. 2 and 3. The holes 28 extend parallel to the longitudinal axis of the fire pot and'are arranged to form the curtain of air along the inner refractory combustion wall Zea by the fact that the holes are positioned to have their outlets directly along the inner Wall 24a. The air curtain provides a lowering of the refractory side wall temperatures.

The heavy oil normally employed as fuel for the burner nozzles is preferably preheated to a range of 120-300 F. depending upon the viscosity of the particular oil being burned. A higher temperature is required for atomization where the viscosity is higher. Further, as heretofore mentioned, the combustion air moving through the plenum chamber 12 is preheated as it travels between the plenum chamber and the combustion chamber 24.

The relative dimensions of the fire pot are important for providing stoichiometric combustion. An example of relative dimensions comprises having an inside combustion chamber diameter of 26%. inches, a total combustion chamber depth as meatured from the end wall 29 to the deepest point along the inside surface of the domeshaped cover 15 of 22 inches, the concave dome also having a 26% inch inside diameter and with a'depth of 4 inches at the center, the choke diameter being 14 inches and the choke depth being 11 inches. The hole 27 in the cover 15 is 1 inch in diameter, while the holes 28 are inch in diameter. There are provided eighteen holes 28 which are circumferentially and equally spaced at the choke end of the combustion chamber. Further, as heretofore mentioned, the choke length is approximately 40 percent of the total length of the combustion chamber as measured from the choke surface edge to the inside top of the dome cover 15. With a fire pot having the above relative dimensions, test results indicated a good fire which approached stoichiometric combustion of:

Smoke reading 1. Blower air pressure 8.3 inch water.

A six hole burner nozzle is employed to atomize the oil fed through the combustion throat, as illustrated in FIGS. 5 and 6, and generally indicated by the numeral 31. The nozzle includes six mixing orifices 32 having an included angle of 50, and opening through an inclined surface 33 that is set 25 from the horizontal or from the transverse axis of said nozzle. An air inlet 34 is provided at the inlet end 35 which communicates with the mixing orifices 32 through atomizing air holes 36. An annular oil inlet groove 37 is arranged at the inlet end 35 of the nozzle and communicates .with the mixing orifices 32 by means of fuel oil holes having an inlet end 38 necked down to an outlet end 39. The axis of the oil holes is offset 20 from the vertical and 45 from the axis of the mixing orifices 32. The mixing orifices 32 and the inlet ends 38 of the oil holes are inch in diameter, while the atomizing air holes 36 and the necked down portion of the oil holes 39 are No. 70 drill. As seen in FIG. 3, a hole 40 is provided for a pilot.

The fire pot of the present invention with the nozzle arrangement as above identified eliminates the formation of carbon deposits on the refractory side walls and any substantial carbon build up on the combustion throat.

From the foregoing, it is seen that the present invention provides an improved burner for boilers capable of burning heavy fuel oils while providing substantially stoichiometric combustion, having greater output with smaller size, and capable of being serviced without being shut down.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention, but it is understood that this application is to be limited only by the scope of the appended claims.

The invention is hereby claimed as follows:

1. A burner for a boiler comprising, a fire pot having a cylindrical body defining a combustion chamber, a domeshaped end wall closing one end of said body and a choke at the other end of said body, a plurality of combustion throats having inner and outer ends and being circumferentially and equally spaced around said body along a single transverse plane spaced closely. adjacent to said end wall, and a burner nozzle for each throat, the longitudinal axis of each burner nozzle and each throat being coaxial and being angularly displaced from a radial line projecting from the longitudinal axis of the fire pot and intersecting the axis of the associated throat and burner nozzle at the inner wall of the fire pot so that each burner nozzle is arranged to direct its spray pattern across the spray pattern of an adjacent spray nozzle, means positively delivering combustion air through said throats, and means for providing an air curtain along the inside walls of said body to cool same, said air curtain means including a plurality of holes extending through said body at the choke end thereof and being parallel to the longitudinal axis of said body, said holes opening adjacent to the inside walls of the body.

2. The combination as defined in claim 1, wherein the a length of the choke is equal to about 40% of the total length of the combustion chamber.

3. The combination as defined in claim 1, wherein said throats are flared open 50 at the inside surface of the combustion chamber.

4. The combination as defined in claim 1, wherein the inner and outer ends of said throats are flared.

5. The combination as defined in claim 1 wherein said 1,924,878 8/33 Parry 11028 dome-shaped end wall is provided with an opening in the 2,242,797 5/41 Lucke 15 8-1.5 center and is in communication with said combustion air 2,893,646 6/59 Batts 239-419 delivery means for creating air movement around the end 2,917,011 12 59 Komer 110 23 wall to provide a cooling action therefor. 5 2,9 5,205 5 1 Boelsma 158-4 6. The combination as defined in claim 1, wherein said 9 701 6/62, -H 1 239-419 combustion throats are venturi-shaped. 3,105,540 10/63 Hardgrove 1 7. The combination as defined in claim 1, wherein each burner nozzle is angularly displaced about from said FOREIGN A NT adlal 10 218,657 12/61 Austria.

References Cited by the Examiner UNITED STATES PATENTS 1,777,411 10/30 Mayr l58--l JAMES W. WESTHAVER, Primary Examiner.

MEYER PERLIN, Examiner.

Claims

1. A BURNER FOR A BOILER COMPRISING, A FIRE POT HAVING A CYLINDRICAL BODY DEFINING A COMBUSTION CHAMBER, A DOMESHAPED END WALL CLOSING ONE END OF SAID BODY AND A CHOKE AT THE OTHER END OF SAID BODY, A PLURALITY OF COMBUSTION THROAT HAVING INNER AND OUTER ENDS AND BEING CIRCUMFERENTIALLY AND EQUALLY SPACED AROUND SAID BODY ALONG A SINGLE TRANSVERSE PLANE SPACED CLOSELY ADJACENT TO SAID END WALL, AND A BURNER NOZZLE FOR EACH THROAT, THE LONGITUDINAL AXIS OF EACH BURNER NOZZLE AND EACH THROAT BEING COAXIAL AND BEING ANGULARLY DISPLACED FROM A RADIAL LINE PROJECTING FROM THE LONGITUDINAL AXIS OF THE FIRE POT AND INTERSECTING THE AXIS OF THE ASSOCIATED THROAT AND BURNER NOZZLE AT THE INNER WALL OF THE FIRE POT SO THAT EACH BURNER NOZZLE IS ARRANGED TO DIRECT ITS SPRAY NOZZLE, ACROSS THE SPRAY PATTERN OF AN ADJACENT SPRAY NOZZLE, MEANS POSITIVELY DELIVERING COMBUSTION AIR THROUGH SAID THROATS, AND MEANS FOR PROVIDING AN AIR CURTAIN ALONG THE INSIDE WALLS OF SAID BODY TO COOL SAME, SAID AIR CURTAIN MEANS INCLUDING A PLURALITY OF HOLES EXTENDING THROUGH SAID BODY AT THE CHOKE END THEREOF AND BEING PARALLEL TO THE LONGITUDINAL AXIS OF SAID BODY, SAID HOLES OPENING ADJACENT TO THE INSIDE WALLS OF THE BODY.